Actually it's properly "lightning stripes (or stripe)", but who's counting?
But - eBay is a good source of decals; I occasionally just put "decal decals" in the search argument of "any word" and just cruise through the "O scale" hits. Pleaurable and it will help you find things that were listed incorrectly (like, ahem, "lightning bolt").
Microscale may have some.
These NYC decals should not be hard to find.